1. Field of the Invention
This invention relates to a sintered ceramic body well-suited for a spark plug insulator which needs an elevated insulation property at high ambient temperature with good thermal conductivity.
2. Description of Prior Art
In a spark plug insulator for an internal combustion engine, a nitride-based sintered ceramic body has been employed since the sintered ceramic body has good thermal conductivity.
The nitride-based sintered ceramic body, however, comes to decrease its electrical insulation when exposed to high ambient temperature, and grows crystals treeing over the surface of the sintered ceramic body when high voltage is applied.
Therefore, it is an object of the invention to provide a sintered ceramic body and spark plug insulator which are capable of maintaining an elevated insulation property at high ambient temperature with good thermal conductivity.